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Canning at high altitudes

Canning is not rocket science, but it is NOT the time to give your culinary creativity full rein. Keep it clean, follow the most current directions, and be sure to adjust canning times for your altitude.

B is for botulism, C is for canning safely

There. We said it. Botulism. The word that scares so many people away from home canning. According to the USDA, botulism is “an illness caused by eating toxin produced by growth of Clostridium botulinum bacteria in moist, low-acid food.”

What is the purpose of careful canning? To destroy such microorganisms in the food and allow you to store and eat it safely.

Some foods are naturally high in acid and will be safe when properly canned in a hot water bath (pickles, berries, peaches, salsa, and chutney for instance) as shown above. High sugar levels in jams and jellies also retard the growth of microorganisms to some extent.

Did you think tomatoes were high acid? They might be, or they might NOT. With the taste for sweeter tomatoes on the rise, the USDA now recommends checking the acidity of tomatoes and figs before choosing a canning method. This is an example of why it’s important to stay up to date with the latest on canning guidelines. Here’s the scoop:

Although tomatoes usually are considered an acid food, some are now known to have pH values slightly above 4.6. Figs also have pH values slightly above 4.6. Therefore, if they are to be canned as acid foods, these products must be acidified to a pH of 4.6 or lower with lemon juice or citric acid. Properly acidified tomatoes and figs are acid foods and can be safely processed in a boiling-water canner.

Low-acid foods need the extra processing of a pressure canner to keep the bacteria at bay. Note the screws and clamps in the pot and lid of the pressure canner in the photo here. Low acid foods include most vegetables such as asparagus, beans, carrots, corn, peas, and pumpkin.

The USDA has an overall guide to canning that clearly outlines which foods need which canning method. Follow the directions to the letter, from cleaning your kitchen, to sterilizing your jars, using correct canning methods and times, cooling your jars, and checking your seals—and you should be botulism free.

If you do suspect any botulism in a jar from your own pantry, or from a friend, use caution when dealing with the spoiled food. The USDA has a sobering reminder, Contact with botulinum toxin can be fatal whether it is ingested or enters through the skin.

Remember the maxim: When in doubt, throw it out and throw it out with care, wearing a pair of rubber gloves.

High altitude canning times

Check your altitude with your local County Extension volunteers such as Master Food Preservers or Master Gardeners. If you have these services in your county they will be listed in the front of your telephone book in the county government section.

Altitude changes for hot water bath canning

Canning recipes assume you live at sea level. When you can above 1,000 feet you need to add more minutes to the processing time in a hot water bath. The extra time is needed because water boils at lower temperatures as the elevation increases, so you need to boil longer to kill the microorganisms. The USDA chart above shows how much the boiling temperatures drop with altitude.